Method for sulfating titaniferous materials



Jan. 1, 1963 L. B. KNUDSEN METHOD FOR SULFATING TITANIFEROUS MATERIALS Filed Aug. 4, 1959 Steuni H Y Condenser Tank INVENTOR Lawrence B. Knudsen W/f 4 4mm AGENT United States Patent Oiilice 3,@?l,435 Patented Jan. 1, 1963 3,071,435 METHOD FUR SULFATING TITANIFEROUS MATERIALS Lawrence B. Knudsen, Middletown, N.J., assiguor to National Lead Company, New York, N.Y., acorporation of New .iersey Filed Aug. 4, 1959, Ser. No. 831,616 9 Claims. (ill. 23-117) The present invention relates in general to sulfating titaniferous materials and more particularly to improved apparatus and method for producing from titaniferous materials a titanium sulfate compound readily soluble in water.

In the production of TiO pigment as currently practiced, titaniferous material such as titaniferous iron ores, titanium bearing slags and flotation concentrates is digested with concentrated H 50 the resulting titanium sulfate compound is recovered from the acid treated product by leaching with H 0, and Ti is precipitated from the resulting titanium sulfate solution by hydrolysis.

The digestion stage is generally carried out on a commercial scale by a batch operation such as that described in the US. patent to Washburn No. 1,889,027. In a typical batch operation the titaniferous material are mixed with concentrated H 50 in a reaction vessel. Mixing may extend over a period of from to minutes whereupon steam and/or set-off, ie a quench liquid plus recycled digestion mud, is added to raise the temperature of the mass to a value closely approximating that at which the H reacts with the titaniferous material. As soon as the reaction between the acid and the titaniferous material is initiated the exothermic nature of the reaction causes it to go with almost explosive rapidity, the amount of heat generated in the large mass of reactants being so great that a large proportion of the water added as set-off and/or produced during sulfation of the titaniferous ore is volatilized and blown out of the reaction tank stack as a great white plume. A major portion of this white plume comprises steam together with ore dust and vaporous S0 S0 H 8 (in the case of slag digestions) and H 80 mist-and accounts for a huge loss of heat as well as air pollution, i.e. objectionable odors, ore dust and acid mist.

The product obtained at the end of the violet reaction period comprises a hard mass, sometimes referred to in the art as digestion cake, containing a major portion of the original titanium content in the form of titanium sulfate. It is conventional practice to follow the foregoing type of digestion procedure with a baking or curing treatment wherein the digestion cake is maintained at an elevated temperature for from 1 to 6 hours to render the maximum amount of titanium values soluble for conversion to an aqueous solution of titanium sulfate.

Although the prevailing method of digesting titaniferous material has been developed to a point where a large quantity of titaniferous material is digested in this manner, it has serveral major disadvantages, namely, the explosive nature of the reaction with the attendant loss of large amounts of heat; the liberation of huge volumes of fumes such that fume control (to prevent air pollution) is prohibitively costly; and the formation of a hard, difi'lcultly soluble, digestion cake which requires, on the average, an over-all curing time of from 3.5 to 4 hours before the maximum amount of soluble TiO required for commercial operations can be recovered.

An object, therefore, of the instant invention is to provide a method for sulfating titaniferous materials which is economical and substantially eliminates offensive and destructive fumes.

Another object of the invention is to provide an improved method for sulfating titaniferous materials at unusualy high temperatures and without the use of water set-o Another object of the invention is to provide a method for digesting titaniferous materials which avoids large losses of heat by utilizing the heat of reaction to preheat the reactants.

A further object of the invention is to provide a method for digesting titaniferous materials so as to produce a digestion product which is readily soluble without previous curing.

A still further object of the invention is to provide an improved apparatus for digesting titaniferous materials at high temperatures with a minimum of heat loss and water consumption and the production of a superior digestion cake.

These and other objects, features and advantages of the invention will be described in the following specification and illustrated in the accompanying drawings in which certain modes of carrying out the present invention are shown.

In the drawings, the FIGURE is a schematic view of a vertical side elevation of one type of apparatus used in carrying out the process of the instant invention.

Before describing the process of the instant invention in detail, it may be said, in general, that the invention relates to the discovery of a process for digesting or sulfating titaniferous materials in a single stage batch operation wherein the heat of the hot reaction vapors, by which is meant both the sensible heat of the hot reaction vapors and the extremely high heat of dilution developed upon contact of the water vapor in the reaction vapors with the reactant acid, is absorbed substantially in toto by the reactants to effect the reaction thereof.

Included among the new results achieved by this process is the formation of a reaction product, sometimes referred to as digestion cake, in a substantially solid but relatively porous state which reaction product, without previous curing treatment, is characterized by an unexpectedly high rate of dissolution in Water. Experimental evidence has shown that digestion cake produced according to the method of the instant invention has a solubility rate of from 10 to 25 times the solubility rate of digestion cake made by earlier techniques. Moreover, TiO recoveries are of the order of from 94 to 98% and hence equal to and better than the Ti0 recoveries obtained from digestion cake prepared by previous techniques and cured for from 3.5 to 4 hours. In addition to these accomplishments may be added the discovery that by following the process steps that characterize the instant invention the reactants are sulfated with large economies in heat and without water set-oif; and the rate of evolution of stack gases including S0 S0 and H 50, mist is reduced to the point that the necessity for fume control is eliminated.

Referring to the drawings, the figure illustrates one mode of apparatus for carrying out the instant invention wherein the reactor indicated generally at 10 is shown as having cylindrical walls 11; a conical top plate 12 having a man-hole for removing the digestion cake; and a bottom plate 13. Extending upwardly from the top plate 12 of the reactor 10 is a reactor stack 14 formed of a relatively non-reactive material and designed for introducing a slurry of the reactants, that is to say, the titaniferous material and acid, into the reactor.

To this end, the top of the stack 14 is provided with a cover 15 through which projects one end of a feed pipe 16 the opposite end of which is connected to a feed tank 17 into which a mixture of ore and acid is fed from a mix tank 18. A valve 19 is provided in the feed pipe 16 for controlling the rate of flow of the slurry from the feed tank 17 to the stack 14. The cover 15 of the stack is also provided with an exhaust pipe 20, the purpose and function of which are hereinafter described.

For effecting absorption of the heat of the hot reaction gases which rise up in the stack from the reactor, the stack is provided with slurry dispersing means indicated generally at 22, the primary function of which is to disperse the slurry of acid and titaniferous material being fed into the stack and thereby expose maximum surface area of the slurry to the hot reaction vapors.

It is of paramount importance, however, that the retention time of the slurry in the stack be so controlled as to prevent the slurry from reacting prematurely and hence form a paste in the stack. Previous experience has shown, for example, that a slurry of acid and titaniferous material will begin to react at temperatures as low as 80 C. and in a very short time a thick paste will be formed which is extremely difiicult to handle. It has now been discovered that reaction of the dispersed slurry can be controlled by controlling the retention time of the slurry in the stack and the temperature differential within the stack. The

slurry retention time is dependent upon such factors as the feed rate of the slurry, the height of the stack and the surface area of the dispersing means and for most satisfactory operations these factors are correlated so that the retention time is within the range of from 1 to 3 seconds for a temperature differential in the stack in the range of from 65 C. to 170 C., the preferred average temperature differential being about 100 C. Under these conditions the ore-acid slurry remains free-flowing throughout its retention time in the reaction stack and at the end of this time is converted substantially immediately to digestion cake.

In the embodiment of the invention shown in the figure, which is to be considered illustrative only and not limiting, the reactor stack comprises a cylinder approximately inches high and 3 inches in diameter while the slurry dispersing means comprises a mass of porcelain balls 23 which may vary from inch to 1 inch in diameter and which are supported in the stack on a suitable grid or screen 24 secured at the bottom of the stack. It will be understood, however, that other types of dispersing elements may be employed in the stack 14 in lieu of porcelain balls, as for example, curled strips of lead foil, lead balls, lead baffies, etc. It is also Within the purview of the invention to effect dispersion of the slurry in the stack by using a liquid spray head, a liquid curtain, or the like.

The temperature differential in the stack is maintained by maintaining the temperature of the hot reaction gases at or adjacent the upper end of the stack preferably in a range from about 80 C. to 135 C. and the temperature of the hot reaction gases at the bottom of the stack preferably in a range from about 200 C. to 250 C. Two controls may be employed for maintaining these temperatures, the one control being the feed rate of the slurry and the other the volume of reaction gases passing up the stack. By increasing the slurry feed rate the relatively cold slurry (30 C. from the feed tank) cools the hot reaction gases in the stack more rapidly thereby lowering the temperature of the gases-and also the absorptive efficiency of the slurry. On the other hand, by decreasing the slurry feed rate the cooling effect of the slurry on the hot reaction vapors in the stack is lessened with the result that the temperature of the gases increases and the absorptive efficiency of the slurry is increased.

The feed rate of the slurry to the stack is readily controlled by operating the valve 19 of the feed line 16 and in the embodiment of the invention disclosed herein for illustrative purposes the slurry feed rate has been varied from 57 grams per minute to 258 grams per minute.

One expedient for controlling the volume of the hot reaction gases passing up through the stack, and hence the temperature of the gases in the stack is to employ stack gas by-pass means which in the embodiment shown comprises a by-pass pipe 25 which enters the reaction tank immediately below the bottom of the stack and is provided with a valve 26 by which the reaction vapors formed within the reactor may be by-passed around the stack. Thus the volume of gases passing up through the stack can be regulated, thereby regulating the temperature of the gases in the stack. By means of these two controls used independently or in conjunction with each other the temperature of the hot reaction vapors at or immediately adjacent the bottom of the stack is held within the range of from 200 C. to 250 C. while the temperatures of the reaction vapors escaping from the exhaust pipe 20 at the upper end of the stack are in the range of from C. to C.

By maintaining the temperature differential of the hot reaction vapors in the stack within the ranges specified above and by controlling the rate of feed of the slurry into the stack so that its retention time at this temperature differential is not in excess of about 3 seconds the slurry flows down freely over the dispersing means and hence is permitted to absorb a maximum amount of the hot reaction vapors and to be heated thereby-the reactants being heated to reaction temperature only at or adjacent the bottom of the stack. It has been found that the temperature of the reaction vapors leaving the upper end of the stack can be used as a guide for establishing approximately that point in the stack where the slurry begins to react.

From the bottom of the stack the reacting slurry descends to the bottom of the reactor 10, the reaction of the ore and acid being substantially completed during descension to the bottom of the reactor. Since the reaction takes place initially in the stack 14 and subsequently in the reactor 10 the stack 14 and the reactor 10 together define a heating zone for heating the dispersed slurry, the stack 14 being hereinafter referred to as the primary heating zone and the reactor 10 as the secondary heating zone.

Supported within the secondary heating zone, defined by the reactor 10, is flow moderating means, indicated generally at 27, comprising a conical member formed preferably from an inert material and provided at its upper end with a conical cap 28. The lower end of the flow moderating means is supported within the secondary heating zone by means of suitable brackets indicated schematically at 29-29.

Intersecting the side wall of the reactor immediately below the screen 24 of the primary heating zone is a valved feed pipe 30 which is connected to a suitable steam supply indicated generally at 31 for feeding steam into the reactor to initiate the reaction of the slurry.

The sulfating of titaniferous materials using the apparatus as hereinabove described is carried out as follows:

Titaniferous material such, for example, ilmenite ore or a mixture of raw ores and ore concentrates, a major portion of which has a particle size of less than 325 mesh, is fed from a suitable source (not shown) into the mix tank 18 in which the titaniferous material is mixed with concentrated sulfuric acid. The latter may vary in acid strength from 93-99% and is fed into the mix tank from a separate source. Measured amounts of titaniferous material and acid are added to the mix tank so that the ratio of acid to the titaniferous material on a wei ht basis is maintained in the ran e of from 1.4-1.7 in the feed tank 17, a specific ratio within this range being selected depending on the quantities and/ or types of sulfates to be produced. The slurry so formed is maintained at about room temperature, that is to say, about 30 C. in the feed tank at which temperature the constituents will not react but will remain in the form of a free-flowing liquid and hence transferable from the feed tank 17 by means of the pipe line 16, and at a controlled rate, to the dispersing means 22 in the reactor stack 14. The flow of slurry through the pipeline may be by gravity feed or may be effected by means of pumps.

Sulfating the slurry in the primary heating zone, identified by the stack 14, is initiated by introducing steam from the source 31 into the reactor at the base of the primary heating zone. The sensible heat of the steam plus the heat of dilution formed by reaction of the water vapor in the steam with the acid in the slurry heats the latter sufficiently to cause the constituents of the slurry to react at the bottom of the primary heating zone and develop hot reaction vapors therein which, in turn, pass upwardly through the dispersing means 22 and serve to heat additional slurry being fed into the upper end of the stack. Once the reaction has been initiated by the steam it is sustained by the heat of the hot reaction vapors developed by the reacting slurry. The high temperature steam is then cut off.

It has been found that the free-flowing slurry may be fed into the stack 14 at rates which range from 57 grams per minute to as high as 258 grams per minute. Moreover, by relating the retention time of the slurry in the primary heating zone with the temperature differential of the hot reaction vapors therein, the constituents of the slurry do not immediately react upon entering the primary heating zone but will trickle down over the dispersing means as a thin film or as discrete droplets as the case may be steadily absorbing the hot reaction vapors and picking up heat as it descends. In this manner maximum surface of the slurry is exposed to the reaction vapors rising in the stack and by the time dispersed slurry reaches the bottom of the primary heating zone, and not before, it has been heated sufficiently by adsorption of the hot reaction vapors to begin to react. At the same time, the hot reaction vapors rising up through the primary heating zone are absorbed substantially in toto by the dispersed slurry such that only minor amounts of heat including minor amounts of S0 S0 and H 80 mist pass out through the exhaust pipe 20.

It will be evident that the reaction of the constituents of the slurry is set otf at the bottom of the primary heating zoneat which the temperature is always in excess of 210 C. and often as high as 250 C. as a'consequence of which the reaction rate is accelerated far beyond rates previously used in the industry and may account in part for the unusually high solubility of the reactant.

Moreover, at these high temperatures the reaction of the constituents of the slurry is completed almost immediately, that is to say, although the slurry is still in liquid form at the lower end of the primary heating zone it is converted in a few seconds to'a substantially solid or semisolid reaction product during its passage from the primary heating zone to the bottom of the secondary heating zone. In this connection the heat of the hot reaction vapor formed in the secondary heating zone by the reacting slurry sustains the reaction already initiated in the slurry. Moreover, acting in conjunction with the heat in the secondary heating zone to complete the reaction of the slurry is the flow moderating means 27 the function of which is to cause the liquid slurry which falls from the lower end of the primary heating zone onto the conical cap 28 of the flow moderator to flow outwardly radially and thence downwardly over the outer surfaces thereof and thus disperse and retard the flow of the reacting slurry from the primary heating zone to the bottom of the secondary heating zone. As a result by the time the reacting slurry has traversed the length of the flow moderator, it is converted to a solid but porous material.

The flow moderator shown in the figure extends the fall time of the slurry to about seconds, i.e. from the time it enters the secondary heating zone until it reaches the bottom thereof. It will be understood however that this particular time interval is illustrative only and not limiting; and that the design of this particular flow moderator may be varied to include such features as radially projecting fins, helixes, spikes, and the like, all of which are contemplated within the scope of the invention.

In order to illustrate the invention further, the following examples are given:

EXAMPLE 1 Using the equipment shown in the figure the following run was made. 2000 grams of solid titaniferous material comprising Maclntyre ore having a T10 content of 45.0% on a weight basis, and a fineness of 1.25% 200 mesh and 5.98% 325 mesh were mixed with 2929 grams of 95.6% H in an acid to ore ratio of 1.40. The temperature of the acid-ore slurry in the feed tank was 30 C. Prior to feeding the slurry into the primary heating zone a temperature differential between the entrance and exit ends of the stack was established at 97 C. and 163 C., respectively, by using auxiliary heating means which in'this instance was steam. The slurry was then introduced and after 4 minutes the steam was shut 01f. At the end of 11 minutes, the temperature of the gases at the bottom of the primary heating zone had reached 202.5 C. whereupon the gases within the secondary heating zone were by-passed so as to reduce the volume of gases passing up through the primary heating zone-and thus lower the temperature of the gases therein. The run was terminated after 30 minutes during which period 4321.5 grams of slurry were sulfated, the slurry feed rate being 146.5 grams per minute. The total reaction vapors which escaped both from the stack and as by-passed vapor, measured as condensate, was 195.5 grams, the rate being 6.5 grams per minute.

Throughout the run the slurry flowed freely over the dispersing means without premature reaction. At the bottom of the stack the slurry reacted rapidly such that the reactants were converted to a substantially solid porous digestion cake by the time the reactants had descended to the bottom of the reactor. During the run, the average temperature differential in the primary heating zone was 101 C. and was maintained as follows:

Temp, Temp, C. C. Slurry Feed, Minutes Top of Bottom of Remarks Primary Primary Heating Heating Zone Zone 97 211 94 207 Steam off. 90 209 89 212 91 213 91 213.5 97 211 105 204. 5 124 202. 5 Vented. 124. 5 207 121 212. 5 118. 5 215 117 214 213. 5 114 213 112 214. 5 115 212. 5 109 212 109 211 106. 5 211 10B 210. 5 105. 5 212.5 105 212.5 104 213 105 212.5 103. 5 216 103. 5 215 111 208 p The digestion cake recovered from the reactor was solid but very porous and was dissolved without previous curing in 4000 cc. of water which was introduced into the tank by a feed pipe at the upper end thereof. The entire cake dissolved readily without mechanical agitation in 70 minutes, the total quantity of digestion solution obtained being 7785 grams.

7 The solution analyzed as follows: Specific gravity 1.493 TiO (reduced) gm./l 5.6 Percent TiO 8.71 Percent H 50 17.00 Percent FeSO 17.79 HeSO /TiO 1.95 FeSo /TiO 2.04 Percent solids 2.255 Grams (solids) 175.6 Grams (solution) 7609.4 Grams (solubilized T 662.8 Percent TiO (digestion solids) 21.65 Grams T102 (in digestion solids) 38.0 Percent recovery 94.6

The recovery of T10 from the ore was 94.6% on a weight basis.

EXAMPLE 2 A second run was made using a slurry consisting of 2000 grams of the Maclntyre ore used in Example 1 and 3138 grams of 95.6% H 50 in an acid-ore ratio of 1.50. Prior to feeding the slurry into the primary heating zone the reactor was preheated by the use of steam until a temperature differential between the upper and lower ends of the primary heating zone was established at 97 C. and 150 C., respectively. The slurry at a temperature of C. was then fed to the primary heating zone for 3 minutes, 40 seconds, whereupon the steam was shut off and 4 minutes later the gases within the reactor were by-passed for 3 consecutive minutes to hold the temperature down in the primary heating zone. The run was terminated after 19 minutes during which period 4628 grams of slurry were sulfated, the slurry feed rate being 248 grams per minute. The reaction vapors which escaped both from the stack and as by-passed vapors, measured as condensate, were 194.6 grams, the rate being 10.3 grams per minute. Throughout the run the slurry flowed freely over the dispersing means without premature reaction but by the time the slurry reached the bottom of the reactor it was converted to a substantially solid but porous digestion .1

cake.

During the run the average temperature differential in the primary heating zone was 917 C. and was maintained as follows:

The digestion cake recovered from the reactor was solid but very porous and dissolved without curing in 4000 co. in water in 55 minutes. A total of 8118 grams of digestion solution was obtained which analyzed as follows:

Specific gravity 1.547 T10 (reduced) gm./l 5

Grams (solution) 7890.6 Grams (solubilized TiO 688.1

Percent TiO (digestion solids) 25.35 Grams T10 (in digestion solids) 57.6 Percent recovery 92.3

The recovery of T102 was 92.3% on a weight basis.

EXAMPLE 3 A third run was made using a slurry fed into the preheating zone at 36 C. and having the following consistency:

1120 grams Quilon ore equivalent to 59.8% TiO on a weight basis.

880 grams slag equivalent to 51.0% TiO on a weight basis.

3,443 grams 98.75% H the ratio of acid to ore-slag mixture being 1.7.

Both the ores and the slag had a fineness of 1.12% 200 mesh and 9.09% 325 mesh. Prior to feeding the slurry into the primary heating zone the latter was preheated by the use of steam to establish a temperature differential of 99 C. at the upper end and 104 C. at the bottom end of the stack. The slurry was then fed into the primary heating zone for 5 minutes, 30 seconds, before the steam was shut 011 and 5 minutes later the gases within the secondary heating zone were bled off for a period of 3 minutes to hold down the temperature in the primary heating zone. The run was terminated after 20 minutes during which period 4951 grams of slurry were sulfated, the slurry feed rate being 267.6 grams per minute. The total reaction vapors which escaped both from the stack and as lay-passed vapors, measured as condensate, was 123.7 grams, the rate being 6.1 grams per minute. Throughout the run the slurry flowed freely over the dispersing means without premature reaction and reacted rapidly at the bottom of the primary heating zone such that the reactants were converted to a substantially solid porous digestion cake 'by the time the reactants had reached the bottom of the secondary heating zone. During the run the average temperature differential in the primary heating zone was 103 C. and was maintained as follows:

7 Temp, Temp,

C. C.- Slurry Feed, Minutes Top 01 Bottom of Remarks Primary Primary Heating Heating Zone Zone 90 198 82 213 74. 5 20-1. 5 217 91 213 Steam 011. 97 198 87 203 78 215 217 103 202 Vented. 121 210 Do. 222 131 226 125 220 121 218 118 214 118 214 138 209 140 203 138 198 The digestion cake recovered from the reactor was solid but very porous and dissolved without curing in 4000 cc. of water in 90 minutes. A total of 8167 grams of digestion solution was obtained which analyzed as follows:

The recovery of T102 was 98.4% on a weight basis.

EXAMPLE 4 A fourth run was made using a slurry comprising 2000 grams of QIT slag having a TiO content of 72.5% o

a weight basis and a particle size of 0.45% 200 mesh and 4.98% 325 mesh; and 3241 grams of 98.9% H the acid-slag ratio being 1.60. As in the preceding runs the primary heating zone was preheated 'by the use of steam to establish a temperature differential of 100 C. at the upper end of the primary heating zone and 120 C. at its bottom end. The slurry was then fed into the primary heating zone for 8 minutes before the steam was shut off. After 14 minutes the gases in the secondary heating zone were by-passed to hold the temperature down in the primary heating zone. This expedient was used again after 22 minutes of operation. The run was terminated after 26 minutes during which period 4338 grams of slurry were sulfated. The reaction vapors which escaped from the stack and as by-passed vapors, measured as condensate, was 157 grams, the rate being 6.0 grams per minute.

Throughout the run the slurry flowed freely over the dispersing means without premature reaction but by the time the slurry reached the bottom of the secondary heating zone it was converted to a substantially solid porous digestion cake. During the run the average temperature differential in the primary heating zone was 100 C. and was maintained as follows:

The digestion cake recovered from the reactor, was solid but very porous and was dissolved without curing 10 in 4000 cc. of water in 135 minutes. 60% of the cake dissolved readily in 30 minutes without agitation and the remainder with slight agitation. A total of 8005 grams of digest solution were obtained which analyzed as follows:

Specific gravity 1.540 TiO (reduced) gm./l. 44.0 Percent TiO 13.21 Percent H 50 28.20 Percent FeSO 5.33 H SO /TiO 2.13

Percent solids 3.577 Grams '(solids) 281.5 Grams (solution) 7723.5 Grams (solubilized TiO 1021.0 Percent TiO (digestion solids) 44.0 Grams T102 (in digestion solids) 123.9 Percent recovery 89.2

The recovery of T18 was 89.2% on a weight basis.

EXAMPLE 5 A fifth run was made using a slurry consisting of 2000 grams of ilmenite ore the TiO content being 52.8% on a weight basis and having a 1i eness of 2.47% 200 mesh and 15.29% 325 mesh; and 3349 grams 95.5% H the acid to ore ratio being 1.60. As in the previous runs a temperature differential was established in the preheating zone by the use of steam prior to introducing the slurry, the temperature at the upper end being 99 C. and 103 C. at the bottom end of the primary heating zone. The slurry was then introduced for 2 minutes before the steam was shut off and 3 minutes later the reaction gases in the secondary heating zone were by-passed for 1 minute so as to hold down the temperature in the primary heating zone. Similarly, gases in the secondary heat ing zone were by-passed during the 9 and 10 minute period. The run was terminated after 16 minutes during which period 4699 grams of slurry were sulfated, the rate being 247 grams per minute. Throughout the run the slurry flowed freely over the dispersing means without premature reaction and reacted almost immediately at or adjacent the bottom of the primary heating Zone such that the reactants were converted to a substantially solid porous digestion cake by the time they had reached the bottom of the reactor. During the run the average temperature differential in the primary heating zone was 104 C. and was maintained as follows:

The digestion cake recovered from the reactor was solid but very porous. It weighed 4700 grams. This was dissolved in 3500 cc. of Water without previous curing and 1 1 produced 8169 grams of digestion solution which analyzed as follows:

12 EXAMPLES 7 AND Additional conventional batch type operations were run using in the one case a 50-50 blend of Maclntyre S ecific avit 1.567 3 gi s gm /1 O ore and Quilon ore, and in the other case straight Mac- -c pcrgent Tioz 9 94 5 intyre ore, the acld-ore ratio being 1.44 in eacn mstancc. pgrcpnt H SO. 21,03 Large quantities of water were used as set-011 and in e a Percent FeSO 19.03 each instance relatlvely huge volumes of gas were dis- H SO /TiO 2.12 charged from the reactor stack at rapid rates. More FeSO /TiO 1.91 over, as in Example 6 the digestion cake was cured Percent solids 1- 4 10 prior to digestion-4n the one case for 2 hours and in Grams (solids) 150.3 the second case for 6 hours. Effective solubilitics were Grams (solution) 8018-7 of the order of five times slower than the effective solu- Grams (solubilized T10 797.1 bilitics of digestion cake made by the process of the Percent Ti0 (digestion solids) 43.6 17 instant invention. Grams TiO (in digestion solids) 65.5 The results of the foregoing experiments are sum- Percent recovery 92.4 marized in the table shown below:

Table I Ex. Titaniierous Acld/ Slurry Max. T C. I'IQO Escape Sol. grn./ Percent No. Material Ore Feed gin] (bottom of Set-01f Gases, nun. Til): min. p.h.z.) tgm.) gm./mi11. 1100.

1. 10 146. 5 216 none 6.5 111. 0 94. e 1. so 248. 5 212. 5 none 10.3 148. 0 e2. 4 1. 207. 6 2% none 6. 1 91. 0 11a. 1 1. 60 167. 0 2351 none 6. 0 G0. 0 80. 1. 60 283. 0 221 none 10. 7 so. 0 v2. 1 do 1.50 batch 159 93.0 17.0 7' MacIntyre Quilon 1. 44 batch 202 133.0 12.0 11.0 (50-50 blend). 0:. u 8 Maclntyre 1.44 batch 303 140.0 12.0 80.7

Maelutyre Ore-massive titaniferous ore mined at Tahawas, New York.

Quilou Ore-beach sands mined in India.

011 Slag-titaniferous slag produced by Quebec Iron and Titanium Ltd. of Canada. Slugs-beneficiated or concentrated. Controls-conventional batch operations.

The recovery of Ti0 from the ore was 92.4% on a Weight basis.

EXAMPLE 6 In order to compare the method of the instant invention, as exemplified by the preceding examples, with earlier methods, hereinafter identified as batch methods, for digesting titaniferous materials a run was made in which the same reaction tank was used minus the primary heating zone. The ore comprised 1500 grams of ihnenite of a fineness of 2.47% 200 mesh and 15.29% 325 mesh and having a T10 content of 52.3% on a weight basis. The acid used to form the ore-acid slurry was 2369 grams of 94.92% H 50 the acid to ore ratio being 1.50. The tank and acid were first heated to 63 C. whereupon the ore was added. 159 grams of H 0 set-off was then added such that the H concentration at reaction Was 89%. The mixture Was agitated by air and mechanical stirring. The reaction period lasted for 13 minutes and the peak temperature reached was 194 C. 3800 grams of digestion cake were recovered from the reactor as a solid, very dense mass. This mass of material was cured for 1 hour and then dissolved in 3000 grams of water. Dissolution of the cake was slow rcquiring 7+ hours the total quantity of digestion solution obtained being 7155 grams. 3% of the cake remained undissolved after 7 hours. The solution analyzed as follows:

Specific gravity 1.542 TiO (reduced) 4.5 Percent T10 9.6 Percent H 50 19.89 Percent FeSO 17.17 H2SO4/Ti02 2.07

Percent solids 2.77

The foregoing examples are based on runs made without using mud return to improve Ti0 recoveries. However, experiments have shown that mud return techniques may be used advantageously in the process of the instant invention. Thus when 3406 grams of titaniferous material were digested at an acid to ore ratio of 1.48 the recovery of TiO without mud return, was 91.53% whereas under the same operating conditions but using mud return the recovery of TiO was raised to 94.94%.

From the foregoing examples it is evident that the method of this invention for sulfating titaniferous ma terials adapts itself to the treatment of ores and slags and mixtures thereof; is economical in utilizing the heat of reaction of the reactants to heat newly added tita uiferous material and in eliminating the need for large amounts of water set-off to initiate and to sustain the reaction. Moreover, it is superior to conventional digestion techniques in that the rate of evolution of obnoxious fumes from the digesting apparatus is so low that the fumes are diluted readily in the atmosphere without constituting a public nuisance; and further the digestion cake is extremely soluble and can be dissolved without previous curing and in unusually short periods of time to give high recoveries of TiO Although the process described above had found specific application in the treatment of titaniferous materials to produce T10 it is also within the purview of 7 the invention to treat other materials amenable to treatment by the method of this invention such as, for example, phosphate rocks for the production of fertilizers.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the means and equivalency range of the appended claims are intended to be embraced therein.

13 I claim:

1. Process for sulfating titaniferous material comprising the steps of: introducing a slurry of titaniferous material and concentrated sulfuric acid, at a temperature below reaction temperature and as a relatively thin stream, into the entrance end of a reaction zone, retaining said slurry therein for from 1 to not more than about 3 seconds, maintaining a minimum temperature differential of 65 C.115 C. between the entrance end and opposite end respectively of said reaction zone to heat and initiate the reaction of said thin stream of slurry and the formation of titanium sulfate and hot reaction vapors in said reaction zone, utilizing said hot reaction vapors to maintain said minimum temperature differential in said reaction zone by exhausting said hot reaction vapors through said thin stream of slurry in the entrance end of said reaction zone, and recovering a porous titanium sulfate digest cake from the opposite end of said reaction zone.

2. Process for sulfating titaniferous material comprising the steps of: introducing a slurry of titaniferous material and concentrated sulfuric acid in a ratio within the range of 1.4:11.7:1, and as a relatively thin stream at a temperature below reaction temperature into the entrance end of a reaction zone, retaining said slurry therein for from 1 to not more than about 3 seconds while maintaining the temperature at the entrance end of said reaction zone within the range of from 65 -135 (3., and at the opposite end of said reaction zone Within the range of from 200 C. to 250 C. to heat and initiate the reaction of said thin stream of slurry and the formation of titanium sulfate and hot reaction vapors in said reaction zone, utilizing said hot reaction vapors to main tain the temperature at the entrance end of said reaction zone within the aforesaid temperature range by exhausting said hot reaction vapors through said thin stream of slurry in the entrance end of said reaction zone and recovering a porous titanium sulfate digest cake from the opposite end of said reaction zone.

3. Process for sulfating titaniferous material comprising the steps of: introducing a slurry of titaniferous material and concentrated sulfuric acid in a ratio within a range of 1.4:11.7:1 at a temperature below reaction temperature and as a relatively thin stream into the entrance end of a reaction zone, dispersing said relatively thin stream of slurry in the entrance end of said reaction zone, retaining said dispersed slurry therein for from 1 to not more than about 3 seconds while maintaining the temperature at the entrance end of said reaction zone within the range of from 65 0-135 C. and at the opposite end of said reaction zone within the range of from ZOO-250 C. to heat and initiate the reaction of said dispersed slurry and the formation of titanium sulfate and hot reaction vapors in said reaction zone, utilizing said hot reaction vapors to maintain the temperature at the entrance end of said reaction zone Within the store said temperature range by exhausting said hot reaction vapors through said dispersed relatively thin stream of slurry in the entrance end of said reaction zone and recovering a porous titanium sulfate digest cake from the opposite end of said reaction zone.

4. Process for sulfating titaniferous materials in a reactor having a primary reaction zone and a secondary reaction zone comprising the steps of: introducing a slurry of titaniferous material and concentrated sulfuric acid, in a ratio Within the range of 1.4:11.7:1, at a temperature below reaction temperature and as a relatively thin stream into the entrance end of said primary reaction zone, dispersing said relatively thin stream of slurry in the entrance end of said primary reaction zone, retaining said dispersed slurry therein for from 1 to not more than about 3 seconds while maintaining a temperature differential of 65 -135 C. between the opposite ends respectively of said primary reaction zone initially to preheat said dispersed slurry, and thereafter to initiate the reaction of said preheated dispersed slurry at a point of maximum temperature in said primary reaction zone and the formation and discharge of titanium sulfate and hot reaction vapors, including water Vapor, from said primary reaction zone into said secondary reaction zone, utilizing said hot reaction vapors, including said water vapor, to maintain said minimum temperature differential in said primary reaction zone by exhausting said hot reaction vapors and Water vapor through said dispersed relatively thin stream of slurry in said primary reaction zone and recovering a porous titanium sulfate digest cake from said secondary reaction zone.

5. Process according to claim 4- in which the flow of titanium sulfate discharged from said primary reaction zone into said secondary reaction zone is retarded.

6. Method according to claim 4 wherein the volume of hot reaction vapors and water vapor exhausted through said dispersed relatively thin slurry is controlled to maintain said minimum temperature differential in said primary reaction zone.

7. In a process for sulfating titaniferous materials wherein a titaniferous ore and concentrated sulfuric acid are heated in a reaction zone to form a titanium-containing reactant and hot reaction vapors, the improvementcomprising: introducing a slurry of said titaniferous material and said acid in a ratio within the range of from 1.4:1l.7:1 at a temperature below reaction temperature and as a relatively thin stream into the entrance end of said reaction zone, dispersing said relatively thin stream of slurry in said reaction zone, retaining said slurry therein for from 1 to not more than about 3 seconds while maintaining a minimum temperature differential of 65 C. to C. between the entrance end and opposite end respectively of said reaction zone to heat and initiate the reaction of said thin stream of slurry and the formation of titanium sulfate and hot reaction vapors in said reaction zone, utilizing said hot reaction vapors to maintain said minimum temperature differential in said reaction zone by passing said hot reaction vapors through and in a direction countercurrent to the direction of flow of said thin stream of dispersed slurry in the entrance end of said reaction zone, and recovering a porous titanium sulfate digest cake from the opposite end of said reaction zone.

8, In a process for sulfating titaniferous materials wherein a titaniferous ore and concentrated sulfuric acid are heated to form a reactant and hot reaction Vapors, the improvement comprising: preparing a slurry of said titaniferous material and said acid in a ratio within the range of 1.4:1-1.7: 1, feeding said slurry in the form of a relatively thin stream and at a temperature below reaction temperature into a primary reaction zone, dispersing said relatively thin stream of slurry in said primary reaction zone, retaining said slurry therein for from 1 to not more than about 3 seconds while maintaining a minimum temperature differential of 65 C.* C. at the opposite ends respectively of said primary reaction zone to heat and initiate the reaction of the dispersed slurry therein and the formation and discharge of titanium sulfate and hot reaction vapors, including water vapor, from said primary reaction zone into a secondary reaction zone, utilizing the hot reaction vapors, including the water vapor, to maintain said minimum temperature differential in said primary reaction zone by passing said hot reaction vapors and water vapor through and in a direction countercurrent to the direction of flow of said dispersed, relatively thin stream of slurry in said primary reaction zone, and recovering a porous titanium sulfate digest cake from said secondary reaction zone.

9. Method according to claim 8 wherein the volume of hot reaction vapors and water vapor passing countereurrently through said dispersed, relatively thin slurry is controlled to maintain said minimum temperature differential in said primary reaction zone, and completing the reaction of the titanium sulfate formed in said primary reaction zone in said secondary reaction zone to form a porous titanium sulfate digest cake therein.

References Cited in the file of this patent UNITED STATES PATENTS Washburn Nov. 29, 1932 Booge et a1. Nov. 2, 1937 Haglund Feb. 14, 1939 McKinney Mar. 17, 1953 Allen et al. June 4, 1957 Cole Apr. 7, 1959 Grifiin May 2, 1961 

1. PROCESS FOR SULFATING TITANIFEROUS MATERIAL COMPRISING THE STEPS OF: INTRODUCING A SLURRY OF TITANIFEROUS MATERIAL AND CONCENTRATED SULFURIC ACID, AT A TEMPERATURE BELOW REACTION TEMPERATURE AND AS A RELATIVELY THIN STREAM, INTO THE ENTRANCE END OF A REACTION ZONE, RETAINING SAID SLURRY THEREIN FOR FROM 1 TO NOT MORE THAN ABOUT 3 SECONDS, MAINTAINING A MINIMUM TEMPERATURE DIFFERENTIAL OF 65*C.-115*C. BETWEEN THE ENTRANCE END AND OPPOSITE END RESPECTIVELY OF SAID REACTION ZONE TO HEAT AND INITIATE THE REACTION OF SAID THIN STREAM OF SLURRY AND THE FORMATION OF TITANIUM SULFATE AND HOT REACTION VAPORS IN SAID REACTION ZONE, UTILIZING SAID HOT REACTION VAPORS TO MAINTAIN SAID MINIMUM TEMPERATURE DIFFERENTTIAL IN SAID REACTION ZONE BY EXHAUSTING SAID HOT REACTION VAPORS THROUGH SAID THIN STREAM OF SLURRY IN THE ENTRANCE END OF SAID REACTION ZONE, AND RECOVERING A POROUS TITANIUM SULFATE DIGEST CAKE FROM THE OPPOSITE END OF SAID REACTION ZONE. 